The missing ArrayAdapter implementation for RecyclerView

ArrayAdapter for RecyclerView

RecyclerView doesn't ship a ready to go RecyclerView.Adapter implementation as ListView did with the ArrayAdapter. This library is this missing ArrayAdapter.

• Easy to use
• Familiar API known from ArrayAdapter for ListView
• Notifies the RecyclerView correctly about changes (notifyItem*()) for smooth animations
• Use swap(List newItems) to swap data. DiffUtils takes care of notifyItem*() calls

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dependencies {
    implementation 'com.pascalwelsch.arrayadapter:arrayadapter:1.3.0'
}

Usage

Given a User pojo with a correct equals/hashCode implementation is used as data type for UserAdapter:

public class UserAdapter extends ArrayAdapter<User, UserAdapter.ViewHolder> {

    public static class ViewHolder extends RecyclerView.ViewHolder {

        private final TextView titleView;

        public ViewHolder(final View itemView) {
            super(itemView);
            titleView = (TextView) itemView.findViewById(R.id.title);
        }
    }

    @Nullable
    @Override
    public Object getItemId(@NonNull final User user) {
        return user.getId();
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, final int position) {
        final User item = getItem(position);
        holder.titleView.setText(item.getName());
    }

    @Override
    public ViewHolder onCreateViewHolder(final ViewGroup parent, final int viewType) {
        final View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.itemview_user, parent, false);
        return new ViewHolder(view);
    }
}

Power User APIs

This ArrayAdapter implementation internally uses DiffUtils to detect changes on items. Two methods are relevant for this magic which you may want to override:

boolean isItemTheSame(old, new)

checks if the id for both items (from getItemId(T)) is equal. Make sure getItemId(T) returns a stable id or at least the item itself.

If the id differs notifyItemRemoved for the old and notifyItemInserted for the new item gets called, resulting in a call to onBindViewHolder.

If the id is the same isContentTheSame(old, new) will be called.

boolean isContentTheSame(old, new)

checks if the visible content if the item has changed. This method should return true when the visual representation of the items is the same. When you only show the name of a User you should return true even when the name fields are equal even when other field are different.

If the content has changed (returns false) notifyItemChanged will be called triggering a call to onBindViewHolder.

If the content is the same (returns true) no notify method is called and onBindViewHolder is not called, too.

By default isContentTheSame performs an equal check on the two item. That's why your pojo should implement equals correctly and it's recommended to use immutable objects.

Override this method for an optimized change detection.

License

Copyright 2017 Pascal Welsch

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.